I am trying modify this setup for two push buttons https://www.arduino.cc/en/Tutorial/Button.

The code seems rather trivial

int yellowButtonPin = 2;
int blueButtonPin = 4;

int yellowButtonState = 0;
int blueButtonState = 0;


void setup(){
  Serial.begin(9600);
  pinMode(yellowButtonPin,INPUT);
  pinMode(blueButtonPin,INPUT);
}

void loop(){
  yellowButtonState = digitalRead(yellowButtonPin);
  blueButtonState = digitalRead(blueButtonPin);
  if (yellowButtonState == HIGH && blueButtonState == HIGH){
    Serial.write(3);
  }
  else if (yellowButtonState == HIGH && blueButtonState == LOW){
    Serial.write(2);
  }
   else if (yellowButtonState == LOW && blueButtonState == HIGH){
    Serial.write(1);
  }
  else {
    Serial.write(0);
  }
}

My problem is that there are several ground pins on the arudino, but only one 5V pin, so I can't just simple double the circuits and connecting the two circuits to different grounds but the same 5V didn't work out, although it seemed to be a good idea. How should I do this properly? To be honest, I actually would want to have three buttons, but I guess going from two to three will be trivial after going from one to two.